The present invention relates to methods and apparatus for treating water/wastewater, and in particular to such methods and apparatus for treating water/wastewater with a variety of contaminant characteristics such as grit, suspended and colloidal solids of organic and inorganic nature, microorganisms and surfactants.
Current water/wastewater treatment systems used to pretreat influent before advanced water treatment stages (such as demineralization and disinfection) vary substantially depending upon the expected water/wastewater influent characteristics. In many applications, these characteristics may not be even known or readily determined. The current water/wastewater pretreatment stages include primary settling, chemical coagulation, filtration and chlorine addition. Each of these methods is designed to operate on a specific type of water contaminant characteristic and, if used properly, produces water of predictable quality. There is no universal water treatment system today capable of reliably removing a wide range of water borne contaminants including grit. Suspended and colloidal solids of organic and inorganic nature, microorganisms and surfactants. Even with a combination of the above named pretreatment units, the water stream would still contain surfactants, micromolecular colloidal solids and oxidizing agents (chlorine) which may be undesirable in the advanced stages of water treatment, particularly demineralization. In addition, the above named and currently available water/wastewater pretreatment stages require constant supervision due to chemical additions and filter back-washing modes, and require substantial manpower for installation and equipment maintenance.
It is therefore an object of the present invention to provide methods and apparatus for treating water/wastewater to remove grit, suspended and colloidal solids of organic and inorganic nature, microorganisms and surfactants.
A further object of the present invention is to provide such methods and apparatus without requiring the use of conventional filters.
Another object of the present invention is to provide such methods and apparatus requiring a minimum of moving parts and chemical additives to reduce maintenance and supply requirements.
Still another object of the present invention is to provide such methods and apparatus capable of operating equally satisfactorily on a raw water source such as brakish surface or ground water, or on gray waste water from laundry, shower and galley sources.
Accordingly, to accomplish these and other objects, the present invention provides methods and apparatus for pretreating water/wastewater in preparation for an advanced treatment stage such as demineralization or disinfection. This pretreatment process is designed to remove a variety of contaminants including grit, suspended and colloidal solids of organic and inorganic nature, microorganisms and surfactants.
Influent water/wastewater is first subjected to a centrifugation process to remove grit and other dense suspended solids. The influent is then collected in a coagulation tank and vigorously stirred to facilitate coagulation. If sufficient coagulating agents or surfactants are not present, chemical coagulants are added. Next the influent is passed through a flocculation tank comprised of a number of vertical baffled and unbaffled chambers which facilitate flocculation and upflow clarification (settling). After coagulation and flocculation, the influent water/wastewater is passed through a high-rate, lamella (parallel plate) separator for final sedimentation.
At this point, the influent water/wastewater is passed through a foam filter to remove colloidal solids. The influent if then collected in a pressurized air saturation tank where air is injected into the water and the air/water solution is pressurized to cause the complete dissolution of the air within the influent. The air saturated influent is then depressurized; the air bubbling out of the solution produces a thick foam which floats contaminants to the surface of the influent. In addition, ozone is introduced and bubbled through the influent to create a thicker, more dense foam by oxidizing organic matter. Lastly, additional ozone is introduced for disinfection purposes. The foam which collects on the surface of the influent is scraped off by conventional means and deposited at the foam filter, replenishing the foam supply in the foam filter.
The novel features believed to be characteristic of the above summarized invention are set forth in particularity in the appended claims. However, a more complete appreciation of the present invention, both as to organization and mode of operation and many of the attendant advantages thereof will result as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings.